It will be very beneficial for those who wants only concentrate on the electron microscope.

1. ELECTRON
MICROSCOPE
Tariq Munir
M.Phil Microbiology

2. DEFINITION
The word microscope is derived from the Greek words
o mikros (small)
o skopeo (look at).
The electron microscope is a type of microscope
that uses a beam of electrons to create an image
of the specimen.

3. BACKGROUND OF E.M
 Light Microscope developed from the Galilean telescope in
17th century.
Earliest microscope invented by Antony van
Leeuwenhoek (1632-1723)
in the 1920s, it was discovered that accelerated electrons
behave in a vacuum much like light.
 Ernst Ruska & Max Knoll built the first transmission
electron microscope (TEM) in 1931
Ruska was awarded the Nobel Prize for Physics in 1986.

4. WORKING OF E.M
The basic steps involved in all EMs:
A stream of high voltage electrons (usually 5-100
KeV) is formed by the Electron Source (usually a
heated tungsten filament) and accelerated in a vacuum
toward the specimen using a positive electrical
potential.
Stream is confined and focused using metal apertures
& magnetic lenses into a thin, focused,
monochromatic beam.
Interactions occur inside the irradiated sample,
affecting the electron beam.

5. SCHEMATIC DIAGRAM OF WORKING

6. TYPES OF ELECTRON MICROSCOPES
1. Transmission Electron
Microscope (TEM) :
The electron beam that
has been partially transmitted
through the very thin (and so
semitransparent for electrons)
specimen carries information
about the structure of the
specimen.

7. TYPES OF ELECTRON MICROSCOPES
2. Scanning Electron
Microscope (SEM):
The Scanning Electron
Microscope (SEM) produces
images by detecting secondary
electrons which are emitted
from the surface due to
excitation by the primary
electron beam.

8. ADVANTAGES
• Powerful magnification.
• In scientific fields including biology and life sciences,
gemology, medical and forensic sciences, metallurgy and
nanotechnologies.
• Technological and industrial applications, such as
semiconductor inspection, computer chip manufacturing,
quality control
• Electron tomography,
• Tissue Localization
• Toxicology

9. DISADVANTAGES
• The main disadvantages are cost, size, maintenance,
researcher training and image artifacts resulting from
specimen preparation.
• This type of microscope is a large, cumbersome, expensive
piece of equipment, extremely sensitive to vibration and
external magnetic fields.
• Upkeep involves maintaining stable voltage supplies, currents
to electromagnetic coils/lens and circulation of cool water so
the samples are not damaged or destroyed from heat given off
during the process of energizing the electrons.

10. .
• Special training is required to learn the involved processes of
specimen preparation, to minimize and recognize preparation-
related artifacts and to operate the microscope itself.
• It needs to be kept in an area large enough to contain the
microscope as well as protect and avoid any unintended
influence on the electrons
• Note:-
Despite these disadvantages, EMs are assets to high-end
research laboratories; this powerful piece of equipment has
resulted in innumerable advances in science and industry.

11. Thank you for your attention